More than 1,200 firefighters are battling the nation's largest wildfire that has charred acre after acre of timber and brush in rugged mountains and canyons of southwestern New Mexico, shrouding parts of the region in smoke.

The blaze maintained its rapid growth Friday through what New Mexico governor Susana Martinez termed "impossible" terrain, as forecasters predicted thunderstorms and dry lightning that could spark even more fires.

Fire authorities said the blaze in the Gila national forest – the largest on record in New Mexico as well as the country's biggest current blaze – had burned through 340 square miles, or 218,000 acres, of terrain.

Firefighters conducted more burnout operations in an effort to corral the erratic blaze that has injured six people, the fire's incident management team said. None of the injuries was serious.

The fire was about 15% contained. Fire information officer Gerry Perry said most of the resources were being focused on the northern and western ends of the fire.

"The wind situation looks a whole lot better, but we're still expecting that we're going to be busy," he said.

The extended forecast called for more hot, dry weather.

So far, the fire has destroyed a dozen cabins and eight outbuildings.

Perry said the fire is close to the community of Mogollon, but the threat is not imminent since firefighters have been working to protect the structures there by clearing debris and applying special fire-resistant wraps.

It's too early for the ecologists, soil scientists and hydrologists to get on the ground to start assessing the damage, but members of the incident management team have estimated that a majority of the fire has left behind moderate and minimal fire scars.

Officials closed the Gila Cliff Dwellings National Monument on Thursday due to smoke generated from the fire. The national park service said the closure will remain in effect until conditions improve.

The wildfire near the Arizona border is fueling experts' predictions that this is a preview of things to come across the west as several states contend with a dangerous mix of wind, low humidity and tinder-dry fuels.

Martinez viewed the fire from a national guard helicopter Thursday and saw the thick smoke shrouding some of the steep canyons that are inaccessible to firefighters. She said that there was no way they could directly attack the flames in the rugged areas of wilderness.

Looking at a blanket of smoke stretching for miles, Martinez used words like "daunting" and "enormous", fitting since fire managers said the blaze could smolder until the region gets significant rainfall.

"It's going to keep going up," she said of the acreage burned. "Be prepared for that."